In the present text, reference is made to a floating LNG plant. Such a floating LNG plant is, for instance, a floating production, storage and offloading unit (FPSO), a floating LNG storage and a regasification unit (FSRU) or a floating power plant comprising LNG tanks (FPGU).
A FPSO, or Floating Production, Storage and Offloading unit is a floating vessel used by the offshore industry for the processing and storage of oil and gas. A FPSO vessel is designed to receive oil or gas produced from a nearby plant or a subsea template, process it, and store it until the oil or the gas can be offloaded onto a tanker or transported through a pipeline.
An FPSO can be obtained by conversion of an oil or gas tanker or can be specifically built for the application. The advantage of a converted FPSO is that using an existing tanker reduces project risks because the vessel is already available and not on the critical path. Project schedules can be reduced to the delivery time of the topsides only and the overall scale of the projects become similar to the typical larger oil conversion FPSO projects.
Solutions for converting a vessel in a LNG FPSO that exist usually propose removal of one or more gas tanks to provide deck space for installing process equipment, needed for the processing of the gas on the vessel. Therefore, converted LNG FPSO's according to the prior art normally have limited remaining storage capacity for storing liquified gas on board of the LNG FPSO.
The international patent application WO2010059059 discloses a device for floating production of LNG and a method for converting an LNG-carrier to a floating device for LNG production. According to WO2010059059 the existing LNG-carrier is provided with an additional projecting hull structure fixed to the ship hull. Thereafter the equipment for the LNG production is arranged in this projecting hull structure. That means that according to WO2010059059 the additional internal space created by adding the projecting hull structure is used to contain at least part of the gas liquefaction process equipment.
The solution according to WO2010059059 has the disadvantage that the gas process equipment is contained in an enclosed space, which can potentially lead to very dangerous situations because of the risk of an explosion in an enclosed space due to leakage of gas from the gas process equipment.
Another disadvantage is linked to the fact that according to the solution of WO2010059059 the gas liquefaction process equipment is installed in the space created at the side of the hull, which leads to a dangerous configuration in view of possible side collisions, with for example a shuttle tanker. Such side collisions would directly damage the gas process equipment in the projecting hull structures.